Voters are choosing congressional nominees in half a dozen state primaries today, from the Pacific Northwest to the Deep South. Those states also run the gamut in their experience with the Affordable Care Act.

Now that the first insurance sign-up period has ended, we thought we'd take this opportunity to explore how the law is playing politically, and gauge what effect Obamacare might have on the midterm elections in November.

To help us with that, we're joined by NPR's Scott Horsley. Good morning.

SCOTT HORSLEY, BYLINE: Good morning.

MONTAGNE: OK. So, in some of the states holding primaries today, policymakers embraced Obamacare, quite enthusiastically. In other states, they did not. What kind of difference has that made?

HORSLEY: Well, it's been a mixed bag, and not always in the ways you might predict. In blue state Oregon, for example, the democratic governor, John Kitzhaber, was fully on board with the Affordable Care Act. But the state-run website was a disaster. Oregon finally had to give up on it and use the federal site. There are five Republicans competing in the primary today in Oregon to challenge Kitzhaber in November. And they're going to try to make him pay for those Affordable Care Act problems.

Then you have a red state like Kentucky, where the Republican Senate Leader Mitch McConnell - one of the leading Obamacare opponents - is competing in a primary today. Kentucky's insurance website actually worked pretty well. Kentucky didn't sign up a whole lot of people for private insurance, but they saw a huge surge in Medicaid enrollments. Kentucky is one of the states that decided to expand Medicaid eligibility under the law.

MONTAGNE: Pennsylvania - which is having a primary today - did not expand Medicaid, though the Republican governor there, Tom Corbett, is pushing an alternative. Four Democrats are competing in that state's primary to challenge Corbett, who's seen as vulnerable. So how does this all play into Affordable Care?

HORSLEY: Corbett is seen as vulnerable, and I want you to listen to a commercial from one of the Democrats who's hoping to take him on in November. This is Pennsylvania Congresswoman Allyson Schwartz.

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HORSLEY: You probably won't hear a lot of political ads like that this year in which a candidate is actually bragging about her role in crafting the Affordable Care Act. Last week, Bill Clinton said Democrats should not run away from the law. Schwartz is one of the few who's actually following that advice, though as of now, she's trailing one of her Democratic rivals in the polls. That's Tom Wolf.

MONTAGNE: Well, Republicans have run a huge number of ads attacking Obamacare. That is their strategy, and has been for a long time. They obviously see a big opportunity. Is there, Scott?

HORSLEY: Well, they're not putting all their eggs in the Obamacare basket. But they do think that could be a very productive basket for them. Robert Blendon, who is a pollster and health policy expert at Harvard, says when you look at the dozen or so states that are going to decide the balance of power in the Senate this fall - several of which are having primaries today - the Affordable Care Act is not likely to play well with voters.

ROBERT BLENDON: Compared to the rest of the country, the voters will be more Republican. The Independents will be a bit more conservative. They'll be older. Many of them may not have benefited at all, as of yet, from the insurance. And they turn out to have more negative views about the legislation.

HORSLEY: Just yesterday, Politico released a poll that focused on contested House and Senate races. Forty-nine percent of the voters in that poll said the Affordable Care Act would be very important in their choice of candidates, and 48 percent favor an outright repeal of the law.

MONTAGNE: And finally, Scott, at this point, more than eight million people have signed up for coverage. I mean, that's much higher than even the Obama administration was aiming for. So has this changed the way voters think about the law?

HORSLEY: That does not seem to have moved the needle very much. Maybe Democratic supporters are not as down in the mouth as they were during November and December. If you've got a pro-Obamacare bumper sticker on your car, maybe you take a sponge and wipe some of the road grime off of it. But it's the opponents who have been much more energized this year. Their bumpers are covered with anti-Obamacare stickers. And they're not peeling them off just because enrollments topped eight million.